1. Field of the Invention
The invention is generally directed to medical catheters and more specifically to the placement of catheters into a patient.
2. Description of Related Art
Catheters are commonplace in the medical field, finding importance in a variety of uses. The term "catheter" is commonly used to identify a tubular instrument that is inserted into a body cavity or orifice, naturally or surgically opened. Vascular catheters, for example, come in many different forms and have many different uses. A vascular catheter typically consists of a hub and tubing or cannula through which fluid flows. The hub may include a flash chamber that allows the individual placing the catheter to see blood in the flash chamber that indicates the catheter has entered a vein. There are different types of vascular catheters. The primary types include the short peripheral, which is typically placed only a short distance (e.g., 2-3 inches) in a vein in the hand or arm of the patient. There are also venous catheters that are longer and include a midline catheter that is placed approximately 6-8 inches in the vein of a patient, and a peripherally inserted central catheter ("PICC") which is placed peripherally, e.g., in the arm of a patient, and fed a significant distance, e.g., to the superior vena cava. Still another type of vascular catheter is the central venous catheter which is typically placed in the internal jugular or subclavien vein, implanted under the skin, tunneled underneath the skin, etc.
One common method of placing a vascular catheter in a patient is through an introducer. In this case, an introducer including a needle, is placed in a patient and into a vein. The needle is then removed, and the catheter is inserted through the introducer into the vein.
A second method of placing a catheter in a patient, often referred to as an Over-The-Needle ("OTN") insertion places the catheter cannula directly over the needle used to introduce the catheter into the vein. The needle is typically connected to a wire or stylet that allows the needle to be removed from the distal or hub end of the catheter cannula once the proximate end of the catheter cannula is placed in the vein. With the needle removed, the catheter is advanced in the vein and placed where desired. The OTN catheter permits the use of a smaller outside diameter needle for a given size outside diameter catheter cannula. The clinical benefit of the OTN approach is the maximization of the size of the catheter placed compared to the size of the needle used. A smaller needle means one can more easily access veins and impart less pain to the patient.
FIGS. 1 and 2 illustrate the different types of vascular catheter introduction methods. FIG. 1 illustrates a Through-The-Introducer ("TTI") insertion method and FIG. 2 illustrates an OTN insertion method. In the TTI type insertion, an introducer sheath 20 and needle 30 are inserted into the vein of a patient. Once inserted, the needle 30 is removed, and the catheter cannula 10 is advanced through the introducer sheath 20. When the catheter cannula is placed through the introducer, the maximum outside diameter of the catheter cannula that is placed is slightly smaller than the inside diameter of the introducer, or, slightly smaller than the outside diameter of the needle. In FIG. 1, for example, at least a 19 gauge needle 30 is needed to place a 20 gauge catheter cannula 10.
In the OTN introduction method, a needle 40 is inserted into a patient, the needle 40 being inside a catheter cannula 10 and having a wire or stylet 50 coupled to a hub 60 at the distal end of the catheter cannula 10. Once the needle 40 and a portion of the catheter cannula 10 are inserted into the patient, the needle 40 is removed from the patient by pulling the hub 60 away from the patient. Once the needle 40 is removed, the catheter cannula 10 is advanced to the desired placement in the patient. FIG. 2 illustrates that a smaller outside diameter needle, e.g., 22 gauge, may be used to place a larger outside diameter catheter cannula, e.g., 20 gauge.